The present invention relates to an air suspension for a vehicle, having at least one air spring per wheel at least one vehicle axle, one pump, at least one accumulator, and one circuit arrangement for connecting these units, the pressure side of the pump being connected to the accumulator or the air springs.
Such an air suspension is described in xe2x80x9cFachkunde Kraftfahrzeugtechnikxe2x80x9d (Technical Book on Automotive Engineering), Europa-Lehrmittel Publishers, 42781 Haan-Gruiten, 25th Ed., page 420. The represented air spring is based on an open compressed-air system, i.e., an accumulator is filled via a pump with fresh air drawn in from the environment and held at a minimum pressure. The compressed air no longer needed in the gas springs is discharged into the environment via a valve. Energy is lost in a number of different ways by releasing compressed air. Among other things, it is the energy that was needed to compress the released air quantity, as well as the energy that was needed for the air purification.
It is an object of the present invention to provide an air suspension system that requires comparably low energy consumption and small unit volume at a high level of efficiency. In addition, the air suspension system is to have short control and response times and only low noise emission.
The above and other beneficial objects of the present invention are achieved by providing an air suspension for a vehicle as described herein. To form a closed compressed-air system, the intake side of the pump is connected via at least one valve to the accumulator or the air springs, and at least the air-guiding interior pump chambers between the intake side and the pressure side of the pump have a pressure-tight arrangement.
Within a closed compressed-air system, the pump represents a type of gas-pressure-tight, pressure-increasing valve that returns the compressed air no longer needed by the air springs to the accumulator instead of releasing it into the environment. Thus, apart from the potential usual leaks, no purified compressed air is lost in this system, and the pump may be configured for relatively small increases in pressure, since, with the exception of air leak compensation, only precompressed air is moved.
The regulating processes of the system are performed between the accumulator and the air springs almost always in a pump-supported manner. Fresh air from outside is only drawn in when the control unit determines that a certain air quantity in the system is not sufficient. In this case, fresh air is drawn in from the surroundings without interrupting the pump process fed until this point, e.g., by the accumulator. For this purpose, the fresh-air connection, in the downstream intake line of which, e.g., an automatically opening non-return valve is located, is situated between the intake side of the pump and the valve or valves that connects or connect the intake side of the pump either to the accumulator or the air springs.
The missing air quantity drawn in from the environment is processed, among other things, by filtering, drying, and, in some instances, deoiling or oiling. The pump support is not necessary when the required spring air pressure is significantly less than the current accumulator pressure. In this case, during a lifting operation, the air flowing to the air springs flows via valves, bypassing the pump.